Study On Key Technology Of The Bistable Piezoelectric Vibration Generator

In order to ensure the continuous electricity supply, it is a critical point to monitor power equipments and power supply equipments to have the ability of fault diagnosis and recovery. Because of a large number, wide distribution, poor working environment for these power equipments, it is difficult to obtain a reliable, durable and stable power supply for wireless sensor network nodes used to monitor power equipments. The bistable piezoelectric vibration generator, based on the piezoelectric effect, is able to convert the vibration energy into electric energy. It can unlimitedly and continuously provide electrical power for wireless sensor network nodes and other low-dissipation electronic devices. That can effectively solve the problem of power supply for wireless sensor network nodes working in the severe environment. To improve power generation capacity of the bistable piezoelectric vibration generator, the research methods of modeling, numerical simulation and experimental verification are used in studying key technology in this paper. The main research contents and results are as follows.(1)The electromechanical coupling model of the single-degree-of-freedom bistable piezoelectric vibration generator is studied. The lumped parameter model of the single-degree-of-freedom bistable piezoelectric vibration generator system is built. The introduction of a model correction factor reduces the lumped parameter model errors caused by the decentralized distribution of the cantilever beam quality. The improved method of calculation model parameters is put forward based on the nonlinear relationship between strain and displacement of the cantilever beam in a large deflection. This method reduces the error caused by nonlinear changes of stiffness coefficient, damping coefficient, electromechanical coupling coefficient. The experimental results show that the improved calculation method of model parameters, improve the prediction accuracy of the model.(2)Dynamic characteristics and power characteristics of the bistable piezoelectric power generation is studied based on the electromechanical coupling of the system. The research results show that the bistable piezoelectric vibration generator system has experienced a low-amplitude periodic motion, a large-amplitude periodic motion, the double periodic motion and chaotic motions, finally returned to a low-amplitude periodic motion, when the excitation frequency increases from small to large. The bistable piezoelectric vibration generator system has experienced a low-amplitude periodic motion, a large-amplitude periodic motion, the chaotic motion and double periodic motions, finally returned to a chaotic motion, when the excitation amplitude increases from small to large. The output open voltage of the system in large-amplitude periodic motion and chaotic motions can meet the requirements of the power management circuit. The effective value of the output open voltage of the bistable piezoelectric vibration generator under the large-amplitude periodic motion is the largest. The experimental results show that under the same load conditions, the output power of the bistable piezoelectric vibration generator under the large-amplitude periodic motion is the largest.(3)To carry out research on optimization amplitude threshold of the bistable piezoelectric vibration generator system for solving difficulties in designing the system amplitude threshold. The amplitude threshold calculation formula of the bistable piezoelectric vibration generator system is deduced based on research on the calculation method of the bistable vibration system threshold. The rules of influence of incentive frequency, magnetic spacing, and cantilever beam geometry parameters on the amplitude threshold are studied. The optimal method about the amplitude threshold is proposed. And the optimization effect is verified by the experiment.(4)A new structure of the two-degree-of-freedom bistable piezoelectric vibration generator is put forward. The excitation amplitude acting on the cantilever beam is amplified for the new added elastic device. The dynamics model of the two-degree-of-freedom bistable piezoelectric vibration generator system is established, and the dynamic characteristics and power characteristics of the system are studied. Research results show that the two-degree-of-freedom bistable piezoelectric vibration generator has smaller amplitude threshold and lower frequency limit values than the single-degree-of-freedom bistable piezoelectric vibration generator. This shows that the two-degree-of-freedom bistable piezoelectric vibration generator is more suitable in collecting the low-frequency and low-amplitude vibration energy.